I’m no expert but I understand that Churchill wanted to send troops before the German invasion; I’m not sure whether that meant effectively invading Norway at the time? I believe Churchill was overruled in this, leading to the eventual counter-invasion; a plan that was never destined to succeed in my humble opinion.

I think that the best that could have been hoped for under the circumstances was to inflict crippling losses on the Germans using warships, submarines, mines and aircraft; this is pretty-much what happened although there were some unfortunate losses on the British side also, such as HMS Glorious. Teaching the Germans just how costly invading Britain could be was the main benefit of Norway; I don’t see how Norway could ever have been held effectively against Germany.